This invention relates to apparatus and methods for delivery of medicament to the respiratory system of a patient. In particular, the invention relates to apparatus and methods for use with a nebulizer.
It is known to use a nebulizer to create an aerosol of medication for delivery into the respiratory system of a patient. Typically the medication is placed in a cup which is held over a reservoir of buffer water. A piezoelectric element is vibrated ultrasonically under the buffer water transferring energy to the water, thus causing an aerosol to be formed in the medication cup. Baffles are provided between the medication cup and the airway in an attempt to ensure large particles of medication rain out on the baffles and drip back down into the medication cup.
However, these nebulizers suffer from a number of disadvantages. In particular, medications have a range of different viscosities, but particle generation is not consistent across the range. Thus the medication particle size is not accurately controlled and a broad range of particles pass into the patient airway. Impaction filters/baffles are often used to attempt to “rain-out” larger particles due to impact of the larger particles with the filters/baffles. Nebulized medication which rains out drips back into the cup only to be nebulized again. This impaction of the nebulized medication may degrade or destroy the medication, and this is particularly the case for long molecular structures, such as proteins.
The medication in the cup is directly exposed to the airway. Therefore the nebulizer must be maintained substantially horizontal at all times to prevent medication spilling out into the patient airway. Also the ventilator pressure may be lost when the medication cup is removed to refill it.
This method of aerosol generation requires a relatively large amount of energy. The response time of aerosol generation is therefore large. A considerable amount of heat is generated during use of the nebulizer, therefore to prevent patient discomfort or injury the nebulizer must be placed away from the patient. This necessitates a long inhalation tube between the nebulizer and the patient, which increases drug loss through rain out along the inhalation tube, and further increases the response time to patient inspiration. Furthermore the generated heat degenerates the medication, which can be particularly harmful to protein based drugs.
This invention is related to apparatus and methods for delivery of medicament to the respiratory system of a patient which overcome at least some of these disadvantages.